The present invention relates to the art of supplying and controlling electrical power to an electromechanical device or motor which converts electrical energy to mechanical energy to produce work. The invention however is not limited to devices which produce mechanical power since the invention concerns the apparatus and method of delivering electrical power generally.
The prior art of electric motor controls consists of either using an alternating current or A.C. electromechanical device or motor together with an A.C. drive control or using a direct current or D.C. motor together with a D.C. drive control. Speed control in the first case generally is accomplished by varying the voltage and frequency of the electrical power supplied to the A.C. motor. Speed control in the second case is accomplished by varying the voltage supplied to the D.C. motor. A.C. controls are however more costly and complicated than the D.C. motor controls. The cost of A.C. control systems is not prohibitive however since the cost of an A.C. motor is generally less than an equivalent D.C. motor and the combination of an A.C. control with an A.C. motor is competitive with the combination of a D.C. control with a D.C. motor. The improvement presented here is an attempt to reduce the cost and complication of motor drive systems generally by the use of a simple electrical circuit apparatus, and an A.C. motor or device.